1. Field of the Invention
The present invention relates to an ink-jet application method employed in a process for producing a display, a biochip, etc. and a display device producing method to which the ink-jet application method is employed. More specifically, the present invention relates to an ink-jet application method employed in a process for applying an application solution on a substrate to be incorporated into a product such as a semiconductor device, a liquid crystal display panel, an organic EL (electroluminescence) display panel, a field emission display panel, etc. and a display device producing method to which the ink-jet application method is employed.
2. Description of the Related Art
In a process for producing a display, a biochip, etc., a film (e.g. functional layer) is formed on a substrate to be incorporated into a product such as a semiconductor device, a liquid crystal display panel, an organic EL (electroluminescence) display panel, a field emission display panel, etc. by spraying drops of an application solution containing a water solution, an inorganic solvent or an organic solvent from a ink-jet nozzle and then applying the application solution on the substrate. This ink-jet application method is mainly employed in a process for forming the film (e.g. process for forming a luminous layer or a color filter layer of a display). The process requires a fine patterning.
A conventional ink-jet application method is disclosed in Japanese Unexamined Patent Publication No. 2003-266003. In the method, in order to restrict a spread of an application solution applied on a substrate within a prescribed range and control a shape of a film formed from the application solution, the following preprocessing is carried out: (1) an ink-attracting process is carried out in a region where the application solution is to be applied; (2) an ink-shedding process is carried out in a region where the application solution is to be not applied; (3) a bank (structural barrier) is formed around a region where the application solution is to be applied.
Especially, the bank is in heavy usage at a time of forming a thick film. In a case where a film or a patterning is formed on a block surrounded by the bank, after one or a plurality of drops of an application solution is sprayed from an ink-jet nozzle and applied on the block, a solid content (film) of the application solution is generated on the block by drying the application solution with a hot plate, an air-spray, a vacuum processing, etc.
However, in the case where the application solution is applied on the substrate on which the bank is formed by using the conventional ink-jet application method, a volume of the application solution is restricted to prevent the application solution from escaping from the block surrounded by the bank. Therefore, a thickness of the solid content of the application solution is far smaller than a height of the bank.
In order to increase the thickness of the solid content, it is cited to increase a concentration of solute (the solid content) included in the application solution. However, in a case where the application solution is applied by using the ink-jet nozzle, the concentration cannot be increased without restriction because an application solution property is adjusted to surface tension and flow resistance which allow the application solution to be easily sprayed from the ink-jet nozzle.
In order to increase the thickness of the solid content, it is cited to increase the height of the bank. However, the height cannot be increased without restriction in view of a structure of the device into which the substrate is incorporated because a film and a layer are usually formed on the bank in a post-process.
In order to increase the thickness of the solid content, it is cited to carry out the ink-shedding process on an upper surface of the bank and spray the application solution in the block surrounded by the bank as much as possible. However, a volume of the application solution cannot be increased without restriction because the sprayed application solution escapes from the block into adjacent blocks.